Over the years, vaccinations that help protect children from infectious diseases such as measles and mumps have saved hundreds of thousands of lives in the United States and prevented millions of hospitalizations, according to the Centers for Disease Control and Prevention.

But it can be tough to know what’s true and what’s not. Can vaccines really make kids sick? Should shots be spaced out as much as possible so their immune systems don’t get overwhelmed?

Here, four common myths about vaccines for kids — and what you need to know.